Lecture 3 Membrane Potentials and Action Potentials

Question 1

Cell Body

Answer 1

Houses the nucleus and other typical cell organelles
The plasma membrane around the cell body is characterized by local potentials
Voltage gated ion channels are NOT characteristic of the cell body membrane

Question 2

Dendrites

Answer 2

Cellular extensions of the neuron
The number is typically a few to many
Dendrites are characterized by the presence of ligand (neurotransmitter) -gated channels
Conduct local potentials

Question 3

This houses the nucleus and other typical cell organelles

Answer 3

The cell body

Question 4

Dendrites conduct

Answer 4

Local potentials

Question 5

Axon

Answer 5

A neuron characterized by a single axon that is variable in length
An extension of the cell body and is typically opposite the side of the cell body where the dendrites are located
An extension of the cell and is covered by the plasma membrane (axolemma)

Question 6

Axolemma

Answer 6

Characterized by the presence of voltage-gated ion channels and the ability to conduct an action potential

Question 7

Distal end of axon

Answer 7

Characterized by the presence of membrane-bound vesicles filled with neurotransmitters

Question 8

Neuron is characterized by

Answer 8

a single axon this is variable in length

Question 9

Myelinated axon looks like

Answer 9

sausage because it is myelinated

Question 10

Telodendria

Answer 10

Means end branches

Question 11

Cell membrane aka

Answer 11

Plasmalemma

Question 12

Cell membrane functions to

Answer 12

maintain separate intracellular and extracellular environments

Question 13

Ion concentrations between intracellular and extracellular environments

Answer 13

Can change depending on whether or not the plasmalemma is permeable to specific ions at given periods of time

Question 14

These ions are more highly concentrated outside the cell

Answer 14

Sodium and chloride

Question 15

Ion more concentrated inside of cell

Answer 15

Potassium

Question 16

Diffusion Potential

Answer 16

A diffusion potential is caused by an ion concentration difference on the two sides of a membrane.
*transitory

Question 17

Nernst Potential

Answer 17

The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane

Question 18

Nernst Equation

Answer 18

E = +- 61 x log [Co]/[Ci]

Question 19

Nernst Equation is used to determine

Answer 19

The diffusion potential across a membrane that exactly opposes the net diffusion of a particular ion through the membrane. It measures the potential for one ion at a time

Question 20

Nernst Equation measures

Answer 20

The potential for one ion at a time

Question 21

To measure the combined potential for more than one ion

Answer 21

The Goldman equation may be used

Question 22

E =

Answer 22

The difference in the electrical potential between inside and outside the neuron
Nernst potential

Question 23

Principal of electrical neutrality

Answer 23

At equilibrium the concentration of ions should be the same

Question 24

Resting membrane potential of nerves

Answer 24

Sodium-Potassium pump

Question 25

Characteristics of action potential

Answer 25

All or none, will occur or won't Self-propagating, each region of depolarization serves to generate action potentials on either side Non-decremental, does not decrease in strength

Question 26

Action potential is all or none

Answer 26

It will either occur or not

Question 27

Action potential is self-propagating

Answer 27

each region of depolarization serves to generate action potentials on either side

Question 28

Action potential is non-decremental

Answer 28

It does not decrease in strength

Question 29

Ion channels

Answer 29

Are channels that allow the passage of ions from one side of the membrane to the other Typically very selective, allowing only one kind of ion to pass through

Question 30

How selective are ion channels?

Answer 30

Very selective, one kind of ion is allowed to pass through

Question 31

Ion channels are open

Answer 31

When certain conditions are met

Question 32

Slow-leak channels are

Answer 32

always open

Question 33

Two types of gated ion channels are

Answer 33

Ligand gated | Voltage gated

Question 34

Voltage gated sodium channels have two gates

Answer 34

Activation Gate | Inactivation Gate

Question 35

Activation gate is closed at

Answer 35

-90mV | The resting potential

Question 36

-90mV

Answer 36

The activation gate is closed and the inactivation gate is opened With the inside of the axon membrane negative relative to the outside

Question 37

Activation gate open, inactivation gate closed

Answer 37

+35mV - -90mV

Question 38

Potassium-gated channels

Answer 38

Have a single gate Gate is closed at a resting potential of -90mV Slow activation opens the gate from +35 mV to -90mV

Question 39

Action Potential Propagation

Answer 39

Steps in the generation of an action potential on a neuron axon membrane 1. Resting Stage 2. Depolarization Stage 3. Repolarization Stage 4. Sodium and potassium conductance

Question 40

Resting Stage

Answer 40

1st step in the generation of an action potential | -90mV

Question 41

Depolarization Stage

Answer 41

Membrane suddenly becomes permeable to sodium ions | Membrane potential may overshoot for large axons

Question 42

Repolarization Stage

Answer 42

Sodium channels close within a few 10,000ths of a second | Potassium channels open more than normal

Question 43

Action Potentials

Answer 43

Current flowing down the inside of an axon at a particular point can continue down the interior of the fiber or cross the membrane at that point.

Question 44

Threshold

Answer 44

Point at which a local potential will elicit an action potential -65mV (highly variable)

Question 45

Action Potential Direction of Propagation

Answer 45

Action potential travels in all directions form the point of stimulation - Orthodromic direction - Antidromic direction

Question 46

Orthodromic Direction

Answer 46

Of an action potential | Direction normally taken

Question 47

Antidromic Direction

Answer 47

Of an action potential | Opposite direction than normally taken

Question 48

As K+ goes out...

Answer 48

Gets more negative because losing +

Question 49

Myelination - 3 parts

Answer 49

1. Sphingomyelin 2. Schwann cell 3. Node of Ranvier

Question 50

Sphingomelin

Answer 50

(myelination) | Lipid, laid down by Schwann cells

Question 51

Schwann cell

Answer 51

(myelination) | Wraps around axons in peripheral nervous system

Question 52

Node of Ranvier

Answer 52

(myelination) | Gaps between Schwann cells, has to jump from one Node of Ranvier, called Saltory conduction

Question 53

Saltatory Conduction

Answer 53

Jumps from one node to the next 1. Increases velocity of nerve transmission 2. Allows 100x less loss of ions and requires little energy for repolarization

Question 54

Fiber diameter

Answer 54

If you increase diameter, can increase surface area, resistance decreases

Question 55

Characteristics of axon that carries signal the fastest

Answer 55

Myelinated axon Large diameter Ex. Skeletal muscle movement

Question 56

Characteristics of axon that carries signal the slowest

Answer 56

Nonmyelinated Small diameter Ex. Pain signals

Question 57

Function of a Schwann cell

Answer 57

to insulate nerve cells

Question 58

Where waves of depolarization occur

Answer 58

Node of Ranvier

Question 59

Absolute refractory period

Answer 59

Right after the action potential | Period during which a second action potential cannot be elicited even with a strong stimulus

Question 60

Relative refractory period

Answer 60

Stronger than normal stimulus can cause action potential | -usually in lab setting

Question 61

Changing ion concentrations

Answer 61

Describe how changes in environmental ion concentrations alter membrane potentials